Yerkes 40' telescope by GLASEducation

Last crawled date: 2 years, 12 months ago

In 1890, this telescope was already partially under construction, and it was planned to be the world's largest telescope. It was, in fact, the world's largest telescope from 1897 (when it was commissioned) to 1909, and it is still the world's largest refractor. The lenses started as glass disks cast by Mantois of Paris and were polished into 40-inch lenses by Alvan Clark and Sons in Cambridgeport, Massachusetts. Warner and Swasey of Cleveland built the mounting for the telescope and a 90-foot diameter dome to house it. They also constructed a 75-foot diameter movable floor that raises astronomers to the telescope eyepiece. This is necessary because the telescope pivots about the middle of the telescope tube: if one end points to a star low on the horizon, the other end (through which you want to look) will be far off the ground. So, the floor rises so that you can be hoisted up to the eyepiece.